Functional initiator for anionic polymerization

ABSTRACT

An ethylenically unsaturated polymer includes at a terminus the radical of an allylic compound that includes a functional group free of active hydrogen atoms that is bonded to the allylic C atom through a S, P, Si or Sn atom and a vinyl aromatic compound. The polymer can be used as a component of a variety of elastomeric compounds used in the production of vulcanizates.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national stage entry of international applicationno. PCT/US2016/056200, filed 8 Oct. 2016, which claims the benefit ofU.S. provisional patent application No. 62/255,612, filed 16 Nov. 2015,the disclosure of which is incorporated herein by reference.

BACKGROUND INFORMATION

Rubber goods such as tire treads often are made from elastomericcompositions that contain one or more reinforcing materials such as, forexample, particulate carbon black and silica; see, e.g., The VanderbiltRubber Handbook, 13th ed. (1990), pp. 603-04.

Good traction and resistance to abrasion are primary considerations fortire treads; however, motor vehicle fuel efficiency concerns argue for aminimization in their rolling resistance, which correlates with areduction in hysteresis and heat build-up during operation of the tire.These considerations are, to a great extent, competing and somewhatcontradictory: treads made from compositions designed to provide goodroad traction usually exhibit increased rolling resistance and viceversa.

Filler(s), polymer(s), and additives typically are chosen so as toprovide an acceptable compromise or balance of the desired properties.Ensuring that reinforcing filler(s) are well dispersed throughout theelastomeric material(s) both enhances processability and acts to improvephysical properties. Dispersion of filler particles can be improved byincreasing their interaction with the elastomer(s) and/or decreasingtheir interaction with each other. Examples of efforts of this typeinclude high temperature mixing in the presence of selectively reactivepromoters, surface oxidation of compounding materials, and surfacegrafting.

The section of a polymer chain from the site of the last crosslink to anend of the polymer chain is a major source of hysteretic losses; thisfree end is not tied to the macromolecular network and thus cannot beinvolved in an efficient elastic recovery process and, as a result,energy transmitted to this section of the polymer (and vulcanizate inwhich such polymer is incorporated) is lost as heat. Ensuring that thesepolymer chain ends are tied to, or otherwise interact well with,reinforcing particulate fillers, is important to many vulcanizatephysical properties such as, for example, reduced hysteresis.

Chemically modifying the polymer, typically at a terminus thereof, isone of the most effective ways of increasing interactivity of fillersand polymers. Terminal chemical modification often occurs by reaction ofa living polymer with a functional terminating agent. Some of thenumerous examples of this approach include U.S. Pat. Nos. 3,109,871,4,647,625, 4,677,153, 5,109,907, 6,977,281, etc., as well as referencescited therein and later publications citing these patents. Some of themost commonly employed synthetic elastomeric materials used in themanufacture of vulcanizates such as tire components include high-cispolybutadiene, often made by processes employing catalysts, andsubstantially random styrene/butadiene interpolymers, often made byprocesses employing anionic initiators. Post-polymerization terminalfunctionalization that can be performed with anionically initiatedpolymers often cannot be performed on coordination catalyzed polymersand, to a lesser extent, vice versa.

Terminal modification also can be provided by means of a functionalinitiator, in isolation or in combination with functional termination.Functional initiators typically are organolithium compounds thatadditionally include functionality, typically functionality thatincludes a nitrogen atom, capable of interacting with one or more typesof particulate filler materials. Many of these functional initiatorshave relatively poor solubility in hydrocarbon solvents of the typecommonly used in anionic (living) polymerizations, and many do notmaintain propagation of living ends as well as more common alkyllithiuminitiators such as n-butyllithium. Both of these characteristics cannegatively impact polymerization rate and efficiency.

This degradation in the ability to propagate living ends can becountered somewhat by conducting polymerizations at lower temperatures,i.e., less than 100° C., often less than 90° C. or even 80° C. Suchtemperature control is not always possible or practical, however,particularly when a continuous or semi-continuous polymerization processis desired.

Functional initiators that retain good initiation performance in anionicpolymerizations conducted at elevated temperatures remain desirable.

SUMMARY

Provided herein is an anionic polymerization method for providingethylenically unsaturated polymers. The method employs a functionalinitiator which efficiently propagates living ends at production scaletemperatures.

In one aspect is provided an initiating compound having the generalformula

where M is a Group 1 metal and Q is a functional group that is free ofactive hydrogen atoms and that is bonded to the allylic C atom of theallyl anion through a S, P, Si or Sn atom.

Initiating compounds such as those defined by general formula (I) can beprovided by reacting a compound defined by the formula RM where M isdefined as above and R is a substituted or unsubstituted hydrocarbylgroup free of active hydrogen atoms with an allylic compound defined bythe general formula

where Q is defined as above.

Also provided is a polymer that includes a radical of a general formula(I) compound at its terminus. Some embodiments of the resulting polymer,in its carbanionic form, can be represented by one of the followinggeneral formulae:

where Q is defined as above and π^(*) represents a carbanionic (living)polymer, typically one which includes polyene mer.

The polymer can be prepared from ethylenically unsaturated monomers,typically including one or more types of polyene, optionally furtherincluding one or more types of vinyl aromatic compounds. In certainembodiments, the polyene(s) can be conjugated dienes, and the resultingconjugated diene mer can incorporated substantially randomly along thepolymer chain. In these and other embodiments, the polymer can besubstantially linear.

The polymer optionally can be provided with terminal functionality (inaddition to that provided by the initiator radical) by reaction with aterminating compound, coupling agent or linking agent.

The polymer can interact with particulate filler such as, but notlimited to, carbon black. Compositions, including vulcanizates, thatinclude particulate fillers and such polymers also are provided, as aremethods of providing and using such compositions.

Methods of providing the polymer, regardless of how characterized, alsoare provided.

Other aspects of the present invention will be apparent to theordinarily skilled artisan from the detailed description that follows.To assist in understanding that description, certain definitions areprovided immediately below, and these are intended to apply throughoutunless the surrounding text explicitly indicates a contrary intention:

-   -   “polymer” means the polymerization product of one or more        monomers and is inclusive of homo-, co-, ter-, tetra-polymers,        etc.;    -   “mer” or “mer unit” means that portion of a polymer derived from        a single reactant molecule (e.g., ethylene mer has the general        formula —CH₂CH₂—);    -   “copolymer” means a polymer that includes mer units derived from        two reactants, typically monomers, and is inclusive of random,        block, segmented, graft, etc., copolymers;    -   “interpolymer” means a polymer that includes mer units derived        from at least two reactants, typically monomers, and is        inclusive of copolymers, terpolymers, tetrapolymers, and the        like;    -   “random interpolymer” means an interpolymer having mer units        derived from each type of constituent monomer incorporated in an        essentially non-repeating manner and being substantially free of        blocks, i.e., segments of three or more of the same mer;    -   “gum Mooney viscosity” is the Mooney viscosity of an uncured        polymer prior to addition of any filler(s);    -   “compound Mooney viscosity” is the Mooney viscosity of a        composition that includes, inter alia, an uncured or partially        cured polymer and particulate filler(s);    -   “substituted” means one containing a heteroatom or functionality        (e.g., hydrocarbyl group) that does not interfere with the        intended purpose of the group in question;    -   “directly bonded” means covalently attached with no intervening        atoms or groups;    -   “polyene” means a molecule with at least two double bonds        located in the longest portion or chain thereof, and        specifically is inclusive of dienes, trienes, and the like;    -   “polydiene” means a polymer that includes mer units from one or        more dienes;    -   “phr” means parts by weight (pbw) per 100 pbw rubber;    -   “radical” or “residue” means the portion of a molecule that        remains after reacting with another molecule, regardless of        whether any atoms are gained or lost as a result of the        reaction;    -   “aryl group” means a phenyl group or a polycyclic aromatic        radical;    -   “ring structure” means a cyclic group; and    -   “terminus” means an end of a polymeric chain;    -   “terminal moiety” means a group or functionality located at a        terminus; and    -   “reactive polymer” means a polymer having at least one site        which, because of the presence of an active terminus, readily        reacts with other molecules, with the term being inclusive of,        inter alia, carbanionic polymers.

Throughout this document, all values given in the form of percentagesare weight percentages (w/w) unless the surrounding text explicitlyindicates a contrary intention. The relevant teachings of all patentdocuments mentioned throughout are incorporated herein by reference.

DETAILED DESCRIPTION

As apparent from the foregoing, polymers provided according to thepresent method can be described or characterized in a variety of ways.

The polymer can be provided by a process in which a general formula (I)compound is used to initiate anionic (living) polymerization of one ormore types of unsaturated monomers. The polymer desirably can includepolyene mer, particularly diene mer units and more particularlyconjugated diene mer, and optionally vinyl aromatic mer units.

The polymer can be elastomeric and can include mer units that includeunsaturation. Unsaturated mer can result from incorporation of polyenes,particularly dienes and trienes (e.g., myrcene). Illustrative polyenesinclude C₄-C₁₂ dienes, particularly conjugated dienes such as, but notlimited to, 1,3-butadiene, isoprene, 1,3-pentadiene,2,3-dimethyl-1,3-butadiene, and 1,3-hexadiene.

Polyenes can incorporate into polymeric chains in more than one way.Especially for polymers targeted for tire tread applications,controlling this manner of incorporation can be desirable. Techniquesfor achieving this control are discussed below.

A polymer chain with an overall 1,2-microstructure, given as a numericalpercentage based on total polyene content, of from ˜10 to ˜80%,optionally from ˜25 to 65%, can be desirable for certain end useapplications. A polymer that has an overall 1,2-microstructure of nomore than ˜50%, preferably no more than ˜45%, more preferably no morethan ˜40%, even more preferably no more than ˜35%, and most preferablyno more than ˜30%, based on total polyene content, is considered to be“substantially linear.”

Directly bonded pendent aromatic groups can be provided by mer unitsderived from vinyl aromatics, particularly the C₈-C₂₀ vinyl aromaticssuch as, e.g., styrene, α-methyl styrene, p-methyl styrene, the vinyltoluenes, the vinyl naphthalenes, and the like. When used in conjunctionwith one or more polyenes, mer units with pendent aromaticity canconstitute from ˜1 to ˜50%, from ˜10 to ˜45%, or from ˜20 to ˜35%, ofthe polymer chain. The microstructure of such interpolymers can berandom, i.e., the mer units derived from each type of constituentmonomer do not form blocks and, instead, are incorporated in anessentially non-repeating manner. Random microstructure can provideparticular benefit in some end use applications such as, e.g., rubbercompositions used in the manufacture of tire treads.

Exemplary elastomers include interpolymers of one or more polyenes andstyrene such as, e.g., poly(styrene-co-butadiene), also known as SBR.

The foregoing types of polymers can be made by emulsion polymerizationor solution polymerization, with the latter affording greater controlwith respect to such properties as randomness, microstructure, etc.Solution polymerizations have been performed since about the mid-20thcentury, so the general aspects thereof are known to the ordinarilyskilled artisan; nevertheless, certain aspects are provided here forconvenience of reference.

Both polar solvents, such as THF, and non-polar solvents can be employedin solution polymerizations, with the latter type being more common inindustrial practice. Examples of non-polar solvents typically employedin anionically initiated solution polymerizations include various C₅-C₁₂cyclic and acyclic alkanes as well as their alkylated derivatives,certain liquid aromatic compounds, and mixtures thereof. The ordinarilyskilled artisan is aware of other useful solvent options andcombinations.

In solution polymerizations, both randomization and vinyl content (i.e.,1,2-microstructure) can be increased by the inclusion in thepolymerization ingredients of a coordinator, usually a polar compound.Up to 90 or more equivalents of coordinator per equivalent of initiatorcan be used, with the amount depending on, for example, the amount ofvinyl content desired, the level of non-polyene monomer employed, thereaction temperature, and nature of the specific coordinator employed.Compounds useful as coordinators include organic compounds that includea heteroatom having a non-bonded pair of electrons, particularly O or N.Examples include dialkyl ethers of mono- and oligo-alkylene glycols;crown ethers; tertiary amines such as tetramethylethylene diamine; THF;THF oligomers; linear and cyclic oligomeric oxolanyl alkanes (see, e.g.,U.S. Pat. No. 4,429,091) such as 2,2-bis(2′-tetrahydrofuryl)propane,di-piperidyl ethane, hexamethylphosphoramide, N,N′-dimethylpiperazine,diazabicyclooctane, diethyl ether, tributylamine, and the like.

Although the ordinarily skilled artisan understands the conditionstypically employed in solution polymerization, a representativedescription is provided for convenience of the reader. The following isbased on a batch process, although extending this description to, e.g.,semi-batch or continuous processes is within the capability of theordinarily skilled artisan. Depending on the nature of the polymerdesired, the particular conditions of the solution polymerization canvary significantly.

Anionic polymerizations typically employ an alkyllithium initiator, suchas n-butyllithium; a so-called multifunctional initiator, which iscapable of forming polymers with more than one living end; or afunctionalized initiator, many of which are poorly soluble in the typesof solvents set forth above and/or unable to maintain good propagationof live ends.

Advantageously, the functional initiators described herein are bothsoluble in the types of organic liquids commonly employed as solvents insolution polymerizations and can maintain propagation of live ends atrelatively high temperatures.

A general formula (I)-type compound can be provided by reacting a RMcompound, with R and M being defined as above, with an allylic compounddefined by general formula (II).

Exemplary RM compounds include any of those where M is one of Na, Li, Kor Cs and R is a substituted or unsubstituted aryl, (cyclo)alkyl,alkaryl, or aralkyl group, most commonly a C₁-C₆ alkyl group, a C₅-C₆cycloalkyl group or a C₆ aryl group. Highly preferred R groups are thosewhich yield RM compounds that are soluble in the polymerization solventsmentioned above such as, for example, n-butyllithium.

Q from the allylic compound defined by general formula (II) is afunctional group that is free of active hydrogen atoms and that isbonded to the allylic C atom of the allyl anion through a S, P, Si or Snatom. Generic formulae for such compounds include

where each R¹ independently is a hydrocarbyl group that is free ofethylenic unsaturation and active H atoms and each R² independently isR¹, a NR¹ ₂ group, or a substituted hydrocarbyl group that is free ofethylenic unsaturation and active H atoms. Preferred R¹ groups includeC₁-C₆ alkyl groups (particularly linear alkyl groups), aryl(particularly phenyl) groups and cycloalkyl (particularly C₅-C₆cycloalkyl), while exemplary R² groups (other than R′) include —NR^(1a)₂ where each R^(1a) represents the aforementioned preferred R¹ groups.

Because of the reactivity of M ions, the initiating compound cannot bemade in the presence of ethylenically unsaturated monomers. Theinitiating compound can be made external to the polymerization vesseland then added thereto when polymerization is ready to be undertaken orby preparing it in the polymerization vessel prior to introduction ofthe monomeric compound(s) thereto.

A batch polymerization typically begins by charging a blend ofmonomer(s) and solvent to a suitable reaction vessel, at a temperatureof from about ˜80° to ˜100° C., more commonly from about ˜40° to ˜50°C., and typically from ˜0° to ˜30° C. The solution then can be heated toa temperature of from about ˜70° to ˜150° C., more commonly from about˜20° to ˜120° C., and typically from ˜50° to ˜100° C. A coordinator (ifused) and initiator are added to the reaction vessel, often are added aspart of a solution or blend. (Alternatively, the monomer(s) andcoordinator can be added to the vessel after introduction of theinitiator. The aforementioned temperature ranges are applicable to thisalternative as well.)

The vessel contents typically are agitated to at least some degree, andthe polymerization preferably is conducted under anaerobic conditionsprovided by an inert protective gas such as N₂, Ar or He. Polymerizationpressure employed may vary widely, although typically a pressure of from˜0.1 to ˜1 MPa is employed.

After the initiating compound and ethylenically unsaturated monomers areintroduced, polymerization is allowed to proceed for a period of timesufficient to result in the formation of the desired functional polymerwhich, in batch processes, typically ranges from ˜0.01 to ˜100 hours,more commonly from ˜0.08 to ˜48 hours, and typically from ˜0.15 to ˜2hours.

The polymerization temperature can vary widely, depending on a varietyof factors, although polymerization vessel temperatures of from ˜20° to˜90° C. are common, but temperatures up to ˜120° C. are possible. Heatcan be removed from the polymerization vessel by external cooling and/orevaporation of the monomer or solvent.

After a desired degree of conversion has been reached, the heat source(if used) can be removed and, if the reaction vessel is to be reservedsolely for polymerizations, the reaction mixture can be removed to apost-polymerization vessel for functionalization and/or quenching. Atthis point, the reaction mixture commonly is referred to as a “polymercement” because of its relatively high concentration of polymer.

A quenched sample of the resulting polymer typically exhibits a gumMooney viscosity (ML₄/100° C.) of from ˜2 to ˜150, more commonly from˜2.5 to ˜125, even more commonly from ˜5 to ˜100, and most commonly from˜10 to ˜75; the foregoing generally correspond to a number averagemolecular weight (Mn) of from 5,000 to 250,000 Daltons, commonly from10,000 to 200,000 Daltons, more commonly from 25,000 to 150,000 Daltons,and most commonly from 50,000 to 125,000 Daltons. The resultinginterpolymer typically has a molecular weight distribution (M_(w)/M_(n),with M_(w) representing weight average molecular weight) of from 1 to10, commonly from 1.5 to 7.5, and more commonly from 2 to 5. (Both Mnand Mw can be determined by GPC using polystyrene standards forcalibration and appropriate Mark-Houwink constants.)

The polymer is considered to include terminal functionality from theradical of the general formula (I) initiator; see general formulas(III-a) and (II-b). However, where additional or other functionality isdesired to enhance interaction with particulate filler, the polymer canbe further functionalized by reaction with an appropriate terminatingreagent, coupling agent and/or linking agent. The ordinarily skilledartisan is familiar with numerous examples of terminal functionalitiesthat can be provided through this type of post-polymerizationfunctionalization. For additional details, the interested reader isdirected to any of U.S. Pat. Nos. 4,015,061, 4,616,069, 4,935,471,5,153,159, 5,149,457, 5,196,138, 5,329,005, 5,496,940, 5,502,131,5,567,815, 5,610,227, 5,663,398, 5,786,441, 6,812,295, 7,153,919,7,816,483, 8,063,153, 8,183,326, 8,586,691, 8,642,706 8,680,210 and9,221,923, etc., as well as references cited in these patents and laterpublications citing these patents. Specific exemplary functionalizingcompounds include SnCl₄, R³ ₃SnCl, R³ ₂SnCl₂, R³SnCl₃, carbodiimides,N-cyclic amides, N,N′-disubstituted cyclic ureas, cyclic amides, cyclicureas, isocyanates, Schiff bases, 4,4′-bis(diethylamino) benzophenone,alkyl thiothiazolines, alkoxysilanes (e.g., Si(OR³)₄, R²Si(OR³)₃, R³₂Si(OR³)₂, etc.) cyclic siloxanes and mixtures thereof. (In theforegoing, each R³ independently is a C₁-C₂₀ alkyl group, C₃-C₂₀cycloalkyl group, C₆-C₂₀ aryl group, or C₇-C₂₀ aralkyl group.) Specificexamples of preferred functionalizing compounds include SnCl₄, tributyltin chloride, dibutyl tin dichloride, and 1,3-dimethyl-2-imidazolidinone(DMI).

Reaction of the foregoing types of compounds with a terminally activepolymer can be performed in less than ˜100 minutes, often fewer than ˜50minutes, at moderate temperatures, e.g., 0° to 75° C. Reaction typicallyoccurs between a C atom of the polymer chain and a Si atom of the cyclicsiloxane, silazane, etc. Because of the reactivity of carbanionic(living) polymers, the molar or equivalent amount of functionalizingcompound need be no greater than essentially 1:1 relative to the amountof initiator employed in the polymerization. although lower and higherratios certainly can be employed.

Quenching can be conducted by stirring the polymer and an activehydrogen-containing compound, such as an alcohol or acid, for up to ˜120minutes at temperatures of from ˜25° to ˜150° C.

The polymer product can be recovered from the polymerization mixtureusing known techniques. For example, a polymerization mixture can bepassed through a heated screw apparatus, such as a desolventizingextruder, in which volatile substances (e.g., low boiling solvents andunreacted monomers) are removed by evaporation at appropriatetemperatures (e.g., ˜100° to ˜170° C.) under no more than atmosphericpressure. Another option involves steam desolvation followed by dryingthe resulting polymer crumbs in a hot air tunnel. Yet another optioninvolves recovering the polymer directly by drying the polymerizationmixture on a drum dryer. Any of the foregoing can be combined withcoagulation with water, alcohol or steam; if coagulation is performed,an elevated temperature drying technique may be desirable.

The resulting polymer can be utilized in a tread stock compound or canbe blended with any conventionally employed tread stock rubber includingnatural rubber and/or non-functionalized synthetic rubbers such as,e.g., one or more of homo- and interpolymers that include justpolyene-derived mer units (e.g., poly(butadiene), poly(isoprene), andcopolymers incorporating butadiene, isoprene, and the like), SBR, butylrubber, neoprene, EPR, EPDM, acrylonitrile/butadiene rubber (NBR),silicone rubber, fluoroelastomers, ethylene/acrylic rubber, EVA,epichlorohydrin rubbers, chlorinated polyethylene rubbers,chlorosulfonated polyethylene rubbers, hydrogenated nitrile rubber,tetrafluoroethylene/propylene rubber and the like. When a functionalizedpolymer(s) is blended with conventional rubber(s), the amounts can varyfrom ˜5 to ˜99% of the total rubber, with the conventional rubber(s)making up the balance of the total rubber. The minimum amount depends toa significant extent on the degree of hysteresis reduction desired.

Amorphous silica (SiO₂) can be utilized as a filler. Silicas aregenerally classified as wet-process, hydrated silicas because they areproduced by a chemical reaction in water, from which they areprecipitated as ultrafine, spherical particles. These primary particlesstrongly associate into aggregates, which in turn combine less stronglyinto agglomerates. “Highly dispersible silica” is any silica having avery substantial ability to de-agglomerate and to disperse in anelastomeric matrix, which can be observed by thin section microscopy.

Surface area gives a reliable measure of the reinforcing character ofdifferent silicas; the Brunauer, Emmet and Teller (“BET”) method(described in J. Am. Chem. Soc., vol. 60, p. 309 et seq.) is arecognized method for determining surface area. BET surface area ofsilicas generally is less than 450 m²/g, and useful ranges of surfaceinclude from ˜32 to ˜400 m²/g, ˜100 to ˜250 m²/g, and ˜150 to ˜220 m²/g.

The pH of the silica filler is generally from ˜5 to ˜7 or slightly over,preferably from ˜5.5 to ˜6.8.

Some commercially available silicas which may be used include Hi-Sil™215, Hi-Sil™ 233, and Hi-Sil™ 190 (PPG Industries, Inc.; Pittsburgh,Pa.). Other suppliers of commercially available silica include GraceDavison (Baltimore, Md.), Degussa Corp. (Parsippany, N.J.), RhodiaSilica Systems (Cranbury, N.J.), and J.M. Huber Corp. (Edison, N.J.).

Silica can be employed in the amount of ˜1 to ˜100 phr, preferably in anamount from ˜5 to ˜80 phr. The useful upper range is limited by the highviscosity that such fillers can impart.

Other useful fillers include all forms of carbon black including, butnot limited to, furnace black, channel blacks and lamp blacks. Morespecifically, examples of the carbon blacks include super abrasionfurnace blacks, high abrasion furnace blacks, fast extrusion furnaceblacks, fine furnace blacks, intermediate super abrasion furnace blacks,semi-reinforcing furnace blacks, medium processing channel blacks, hardprocessing channel blacks, conducting channel blacks, and acetyleneblacks; mixtures of two or more of these can be used. Carbon blackshaving a surface area (EMSA) of at least 20 m²/g, preferably at least˜35 m²/g, are preferred; surface area values can be determined by ASTMD-1765 using the CTAB technique. The carbon blacks may be in pelletizedform or an unpelletized flocculent mass, although unpelletized carbonblack can be preferred for use in certain mixers.

The amount of carbon black can be up to ˜50 phr, with ˜5 to ˜40 phrbeing typical. When carbon black is used with silica, the amount ofsilica can be decreased to as low as ˜1 phr; as the amount of silicadecreases, lesser amounts of the processing aids, plus silane if any,can be employed.

Elastomeric compounds typically are filled to a volume fraction, whichis the total volume of filler(s) added divided by the total volume ofthe elastomeric stock, of ˜25%; accordingly, typical (combined) amountsof reinforcing fillers, i.e., silica and carbon black, is ˜30 to 100phr.

When silica is employed as a reinforcing filler, addition of a couplingagent such as a silane is customary so as to ensure good mixing in, andinteraction with, the elastomer(s). Generally, the amount of silane thatis added ranges between ˜4 and 20%, based on the weight of silica fillerpresent in the elastomeric compound.

Coupling agents are compounds which include a functional group capableof bonding physically and/or chemically with a group on the surface ofthe silica filler (e.g., surface silanol groups) and a functional groupcapable of bonding with the elastomer (e.g., via a sulfurcontaininglinkage). Such coupling agents include organosilanes, in particularpolysulfurized alkoxysilanes (see, e.g., U.S. Pat. Nos. 3,873,489,3,978,103, 3,997,581, 4,002,594, 5,580,919, 5,583,245, 5,663,396,5,684,171, 5,684,172, 5,696,197, etc.) or polyorganosiloxanes bearingthe types of functionalities mentioned above. An exemplary couplingagent is bis[3-(triethoxysilyl)propyl]tetrasulfide. One or more couplingagents can be added to the elastomeric (rubber) composition if desired,although the functionalized polymer of the present invention can beutilized in elastomeric compositions that do not include such couplingagents.

Addition of a processing aid can be used to reduce the amount of silaneemployed. See, e.g., U.S. Pat. No. 6,525,118 for a description of fattyacid esters of sugars used as processing aids. Additional fillers usefulas processing aids include, but are not limited to, mineral fillers,such as clay (hydrous aluminum silicate), talc (hydrous magnesiumsilicate), and mica as well as non-mineral fillers such as urea andsodium sulfate. Preferred micas contain principally alumina, silica andpotash, although other variants also can be useful. The additionalfillers can be utilized in an amount of up to ˜40 phr, typically up to˜20 phr.

Other conventional rubber additives also can be added. These include,for example, process oils, plasticizers, anti-degradants such asantioxidants and antiozonants, curing agents and the like.

All of the ingredients can be mixed using standard equipment such as,e.g., Banbury or Brabender mixers. Typically, mixing occurs in two ormore stages. During the first stage (often referred to as themasterbatch stage), mixing typically is begun at temperatures of ˜120°to ˜130° C. and increases until a so-called drop temperature, typically˜165° C., is reached.

Where a formulation includes silica, a separate re-mill stage often isemployed for separate addition of the silane component(s). This stageoften is performed at temperatures similar to, although often slightlylower than, those employed in the masterbatch stage, i.e., ramping from˜90° C. to a drop temperature of ˜150° C.

Reinforced rubber compounds conventionally are cured with about 0.2 toabout 5 phr of one or more known vulcanizing agents such as, forexample, sulfur or peroxide-based curing systems. For a generaldisclosure of suitable vulcanizing agents, the interested reader isdirected to an overview such as that provided in Kirk-Othmer,Encyclopedia of Chem. Tech., 3d ed., (Wiley Interscience, New York,1982), vol. 20, pp. 365-468. Vulcanizing agents, accelerators, etc., areadded at a final mixing stage. To ensure that onset of vulcanizationdoes not occur prematurely, this mixing step often is done at lowertemperatures, e.g., starting at ˜60° to ˜65° C. and not going higherthan ˜105° to ˜110° C.

Certain tests have come to be recognized as correlating certain physicalproperties of vulcanizates with performance of products, particularlytire treads, made therefrom. For example, reductions in hysteresis (heatbuild-up during operation) have been found to correlate with higherrebound values and lower loss tangent values (tan δ) at hightemperature, better handling performance often correlates with higherelastic modulus values at high temperature and strain, ice traction hasbeen found to correlate with lower modulus values at low temperatures,etc. (In the foregoing, “high temperature” typically is considered to be˜50° to 65° C. while “low temperature” is considered to be ˜0° to ˜25°C.) Further, as a general rule, the lowest possible ∴ tan δ generally isdesirable.

Various embodiments of the present invention have been provided by wayof example and not limitation. As evident from the foregoingdescriptions, general preferences regarding features, ranges, numericallimitations and embodiments are to the extent feasible, as long as notinterfering or incompatible, envisioned as being capable of beingcombined with other such generally preferred features, ranges, numericallimitations and embodiments.

The following non-limiting, illustrative examples provide the readerwith detailed conditions and materials that can be useful in thepractice of the present invention. These examples employ 1,3-butadieneas an exemplary polyene and styrene as an exemplary vinyl aromaticcompound due to a variety of factors including cost, availability,ability to handle and, most importantly, ability to make internalcomparisons as well as comparisons against previously reported polymers.The ordinarily skilled artisan will be able to extend these examples toa variety of homo- and interpolymers.

EXAMPLES

In the examples, dried glass vessels previously sealed with extractedseptum liners and perforated crown caps under a positive N₂ purge wereused for all preparations. Butadiene solution (19.1% in hexane), styrene(33.5% in hexane), hexane, n-butyllithium (n-BuLi, 1.6 M in hexane),2,2-bis(2′-tetrahydrofuryl)propane (1.6 M solution in hexane, storedover CaH₂), tin(IV) chloride (0.25 M solution in hexane) and butylatedhydroxytoluene (BHT) solution in hexane were used.

Commercially available reagents and starting materials included thefollowing, all of which used without further purification unlessotherwise noted in a specific example:

-   -   from Sigma-Aldrich Co. (St. Louis, Mo.)—allyl methyl sulfide,        allyl(diethylamino)dimethylsilane, allyltrimethylsilane,        allyltributylstannane, and allyldiphenylphosphine;    -   from Gelest Inc. (Morrisville,        Pa.)—3-(1,3-dimethylbutylidene)aminopropyltriethoxysilane (AP3E,        3.0 M) and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECH3M;        4.3 M).

Testing data in the Examples was performed on filled compositions madeaccording to the formulations shown in Tables 1a (a formulationemploying only silica as a particulate filler) and 1b (a formulationemploying only carbon black as a particulate filler). In these tables,N-phenyl-N′-(1,3-dimethylbutyl)-p-phenyldiamine acts as an antioxidantwhile 2,2′-dithiobisbenzothiazole, N-t-butylbenzothiazole-2-sulfenamide,and N,N′-diphenylguanidine act as accelerators. These formulations areused to permit evaluation of functionalized polymers with specificparticulate fillers, but this should not be considered limiting becausemixtures of carbon black and silica, as well as the presence ofadditional types of particulate fillers, are envisioned.

TABLE 1A Composition for vulcanizates, silica filler Amount (phr)Masterbatch synthesized polymer 80 poly(isoprene) (natural rubber) 20silica 52.5 wax 2 N-phenyl-N′-(1,3-dimethylbutyl)-p-phenyldiamine 0.95stearic acid 2 processing oil (low PCA content) 10 Re-mill silica 2.5silane 5 Final sulfur 1.5 ZnO 2.5 2,2′-dithiobisbenzothiazole 2.0N-t-butylbenzothiazole-2-sulfenamide 0.7 N,N′-diphenylguanidine 0.2TOTAL 183.05

TABLE 1B Composition for vulcanizates, carbon black filler Amount (phr)Masterbatch synthesized polymer 100 carbon black (N343 type) 50 wax 2N-phenyl-N′-(1,3-dimethylbutyl)-p-phenyldiamine 0.95 stearic acid 2processing oil (low PCA content) 10 Final sulfur 1.5 ZnO 2.52,2′-dithiobisbenzothiazole 0.5 N-t-butylbenzothiazole-2-sulfenamide 0.5N,N′-diphenylguanidine 0.3 TOTAL 170.25

Data corresponding to “Bound rubber” were determined using a procedurebased on that described by J. J. Brennan et al., Rubber Chem. and Tech.,40, 817 (1967).

Molecular weight data were determined via GPC, as described above.

Gum and compound Mooney viscosity (ML₁₊₄) values were determined with anAlpha Technologies™ Mooney viscometer (large rotor) using a one-minutewarm-up time and a 4-minute running time; t₈₀ is the time (in sec,beginning at the point that disk of the viscometer is stopped) necessaryfor 80% of the Mooney viscosity to decay; tensile mechanical propertieswere determined using the standard procedure described in ASTM-D412;hysteresis (tan δ) data were obtained from dynamic experiments conductedat 60° C. and 10 Hz (strain sweep).

Examples 1-4: Control Polymerizations, n-Butyllithium

To a N₂-purged reactor equipped with a stirrer was added 1.36 kg hexane,0.45 kg styrene solution, and 3.14 kg butadiene solution. The reactorwas charged with 3.6 mL n-BuLi solution, followed by 1.1 mL2,2-bis(2′-tetrahydrofuryl)propane solution. The reactor jacket washeated to 50° C. and, after ˜33 minutes, the batch temperature peaked at˜65° C.

After an additional ˜30 minutes, portions of the polymer cement weretransferred to four glass bottles. To one of the bottles (designatedsample 1 below) was added isopropanol so as to quench the living polymerwhile, to the other bottles, were added

-   -   sample 2-0.17 mL AP3E,    -   sample 3-0.12 mL ECH3M, and    -   sample 4-0.5 mL SnCl₄ solution (0.25 M in hexane).        Each bottle was placed in a 50° C. bath. After ˜30 minutes, the        bottles were removed, and the contents of each were separately        coagulated in isopropanol containing BHT before being drum        dried.

Certain properties of these polymers are summarized below in Table 2.

Examples 5-8: Polymerizations, P-Allylic Initiator

To a mixture of 10 mL dried cyclohexane and 1.18 mLallyldiphenylphosphine (4.63 M) was added 3.6 mL n-BuLi solutionfollowed by 1.1 mL 2,2-bis(2′-tetrahydrofuryl)propane solution. Thecontents were allowed to stir at room temperature for an additional ˜15minutes.

The procedure from Examples 1-4 was essentially repeated with theforegoing functional initiator solution being added in place of theseparate n-BuLi and 2,2-bis(2′-tetrahydrofuryl)propane solutions. Thistime, the batch temperature peaked at ˜66° C. after ˜43 minutes.

After an additional ˜30 minutes, portions of the polymer cement weretransferred to four glass bottles. Samples 5-8 were quenched or reactedthe same as, respectively, samples 1-4. The bottles were processedsimilarly to those from Examples 1-4.

Certain properties of these polymers are summarized below in Table 2.

Examples 9-12: Polymerizations, Sn-Allylic Initiator

To a mixture of 10 mL dried cyclohexane and 1.7 mL allyltributylstannane(3.22 M) was added 3.6 mL n-BuLi solution followed by 1.1 mL2,2-bis(2′-tetrahydrofuryl)propane solution. The contents were allowedto stir at room temperature for an additional ˜15 minutes.

The procedure from Examples 1-4 was essentially repeated with theforegoing functional initiator solution being added in place of theseparate n-BuLi and 2,2-bis(2′-tetrahydrofuryl)propane solutions. Thistime, the batch temperature peaked at ˜65° C. after ˜35 minutes.

After an additional ˜30 minutes, portions of the polymer cement weretransferred to four glass bottles. Samples 9-12 were quenched or reactedthe same as, respectively, samples 1-4. The bottles were processedsimilarly to those from Examples 1-4.

Certain properties of these polymers are summarized below in Table 2.

Examples 13-16: Polymerizations, Si-Allylic Initiator

To a mixture of 10 mL dried cyclohexane and 0.87 mL allyltrimethylsilane(6.29 M) was added 3.6 mL n-BuLi solution followed by 1.1 mL2,2-bis(2′-tetrahydrofuryl)propane solution. The contents were allowedto stir at room temperature for an additional ˜15 minutes.

The procedure from Examples 1-4 was essentially repeated with theforegoing functional initiator solution being added in place of theseparate n-BuLi and 2,2-bis(2′-tetrahydrofuryl)propane solutions. Thistime, the batch temperature peaked at ˜67° C. after ˜27 minutes.

After an additional ˜30 minutes, portions of the polymer cement weretransferred to four glass bottles. Samples 13-16 were quenched orreacted the same as, respectively, samples 1-4. The bottles wereprocessed similarly to those from Examples 1-4.

Certain properties of these polymers are summarized below in Table 2.

Examples 17-20: Polymerizations, Alternative Si-Allylic Initiator

To a mixture of 10 mL dried cyclohexane and 1.18 mLallyl(diethylamino)dimethylsilane (4.64 M) was added 3.6 mL n-BuLisolution followed by 1.1 mL 2,2-bis(2′-tetrahydrofuryl)propane solution.The contents were allowed to stir at room temperature for an additional˜15 minutes.

The procedure from Examples 1-4 was essentially repeated with theforegoing functional initiator solution being added in place of theseparate n-BuLi and 2,2-bis(2′-tetrahydrofuryl)propane solutions. Thistime, the batch temperature peaked at ˜65° C. after ˜33 minutes.

After an additional ˜30 minutes, portions of the polymer cement weretransferred to four glass bottles. Samples 17-20 were quenched orreacted the same as, respectively, samples 1-4. The bottles wereprocessed similarly to those from Examples 1-4.

Certain properties of these polymers are summarized below in Table 2.

Examples 21-24: Polymerizations, S-Allylic Initiator

To a mixture of 10 mL dried cyclohexane and 0.6 mL allyl methyl sulfide(9.10 M) was added 3.6 mL n-BuLi solution followed by 1.1 mL2,2-bis(2′-tetrahydrofuryl)propane solution. The contents were allowedto stir at room temperature for an additional ˜15 minutes.

The procedure from Examples 1-4 was essentially repeated with theforegoing functional initiator solution being added in place of theseparate n-BuLi and 2,2-bis(2′-tetrahydrofuryl)propane solutions. Thistime, the batch temperature peaked at ˜69° C. after ˜33 minutes.

After an additional ˜30 minutes, portions of the polymer cement weretransferred to four glass bottles. Samples 5-8 were quenched or reactedthe same as, respectively, samples 1-4. The bottles were processedsimilarly to those from Examples 1-4.

Certain properties of these polymers are summarized below in Table 2.

TABLE 2 Polymer properties M_(n) M_(p) % T_(g) ML₁₊₄ @ t₈₀ (kg/mol)(kg/mol) M_(w)/M_(n) coupling (° C.) 100° C. (sec) sample 1 118 121 1.060 −38.0 12.7 0.94 sample 2 145 121 1.40 36.1 −36.9 18.6 1.10 sample 3143 121 1.29 31.5 −37.3 29.4 1.35 sample 4 289 399 1.27 88.1 −38.0 92.66.39 sample 5 136 165 1.16 0 −45.5 29.4 1.03 sample 6 149 165 1.22 11.9−46.3 39.2 1.23 sample 7 166 167 1.32 27.5 −45.7 55.4 1.58 sample 8 265487 1.49 73.0 −45.3 107.2 6.03 sample 9 149 156 1.06 0 −37.3 — — sample10 166 157 1.32 20.8 −40.0 — — sample 11 174 157 1.24 24.9 −38.0 — —sample 12 292 477 1.40 75.0 −38.9 — — sample 13 111 113 1.06 2.6 −38.5 —— sample 14 136 113 1.41 34.2 −38.5 — — sample 15 136 114 1.31 33.7−39.0 — — sample 16 270 376 1.28 87.5 −39.3 — — sample 17 116 119 1.06 0−38.7 — — sample 18 129 118 1.33 35.0 −39.0 — — sample 19 138 119 1.2831.0 −38.9 — — sample 20 242 394 1.49 90.0 −39.6 — — sample 21 118 1271.07 0 −40.5 — — sample 22 120 127 1.20 13.5 −39.8 — — sample 23 147 1281.33 32.0 −40.0 — — sample 24 265 410 1.39 82.8 −39.9 — —

Examples 25-48: Vulcanizates

Using the formulations from Table 1a and Table 1b above, vulcanizableelastomeric compounds containing reinforcing fillers were prepared fromsamples 5-8 and 16-24. Compounds were cured for ˜15 minutes at 171° C.to provide vulcanizates 25-48.

Results of physical testing on vulcanizates made from these polymers aresummarized below in Tables 3a-3c.

TABLE 3A Compound and vulcanizate properties, P-allylic initiatedpolymer 25 26 27 28 29 30 31 32 synthetic polymer (sample no.) 5 6 7 8 56 7 8 compound formulation (Table no.) 1a 1a 1a 1a 1b 1b 1b 1b Boundrubber (%) 20.1 69.4 75.5 28.0 11.7 43.5 30.1 31.7 ML₁₊₄ @ 130° C.(final) 29.1 67.4 70.0 53.0 35.2 82.1 96.0 58.9 Strain sweep (60° C., 10Hz, final) tan δ 0.1456 0.0825 0.0684 0.1136 0.1903 0.1385 0.1398 0.1159Δ tan δ 0.0687 0.0226 0.0130 0.0460 0.1084 0.0670 0.0624 0.0369

TABLE 3B Compound and vulcanizate properties, Si-allylic initiatedpolymer 33 34 35 36 37 38 39 40 synthetic polymer (sample no.) 16 17 1819 16 17 18 19 compound formulation (Table no.) 1a 1a 1a 1a 1b 1b 1b 1bBound rubber (%) 17.7 69.7 76.5 25.3 7.3 46.5 27.2 26.5 ML₁₊₄ @ 130° C.(final) 16.4 52.3 53.9 40.1 20.3 63.9 78.2 38.9 Strain sweep (60° C., 10Hz, final) tan δ 0.1506 0.0777 0.0652 0.1211 0.2248 0.1487 0.1635 0.1231Δ tan δ 0.1146 0.0515 0.0374 0.0531 0.1406 0.0674 0.0814 0.0317

TABLE 3C Compound and vulcanizate properties, S-allylic initiatedpolymer 41 42 43 44 45 46 47 48 synthetic polymer (sample no.) 21 22 2324 21 22 23 24 compound formulation (Table no.) 1a 1a 1a 1a 1b 1b 1b 1bBound rubber (%) 17.8 66.3 71.8 22.8 11.2 45.4 26.3 31.8 ML₁₊₄ @ 130° C.(final) 20.3 53.2 55.4 44.4 20.3 53.2 55.4 44.4 Strain sweep (60° C., 10Hz, final) tan δ 0.1541 0.0790 0.0627 0.1217 0.2067 0.1320 0.1404 0.1074Δ tan δ 0.0775 0.0250 0.0105 0.0541 0.1291 0.0595 0.0668 0.0281

That which is claimed is:
 1. A process for providing a polymer thatcomprises ethylenic unsaturation, comprising: a) providing an initiatingcompound having the general formula

where M is a Group 1 metal and Q is a functional group that is free ofactive hydrogen atoms and that is bonded to the allylic C atom of theallyl anion through a atom; b) introducing said initiating compound to areaction vessel that comprises one or more organic liquids and one ormore ethylenically unsaturated compounds which comprise at least onepolyene; c) allowing said one or more ethylenically unsaturatedcompounds to polymerize, thereby providing said polymer; and d)optionally, while said polymer is in carbanionic form, allowing it toreact with a terminating compound, coupling agent or linking agent so asto provide terminal functionality to said polymer.
 2. The process ofclaim 1 wherein Q is a R¹S group where R¹ is a hydrocarbyl group that isfree of ethylenic unsaturation and active H atoms.
 3. The process ofclaim 2 wherein R¹ is a C₁-C₆ alkyl group.
 4. The process of claim 1wherein said at least one polyene comprises one or more conjugateddienes.
 5. The process of claim 4 wherein said one or more ethylenicallyunsaturated compounds further comprises at least one vinyl aromaticcompound.
 6. The process of claim 1 wherein said one or more organicliquids comprise at least one C₅-C₁₂ acyclic alkane.
 7. The process ofclaim 6 wherein said one or more organic liquids is at least one C₅-C₁₂acyclic alkane.
 8. The process of claim 1 further comprising (e)recovering and isolating said polymer and (f) blending said polymer withingredients that comprise at least one particulate filler so as toprovide a rubber compound.
 9. The process of claim 8 further comprisingvulcanizing said rubber compound so as to provide a vulcanizate, saidvulcanizate optionally being a tire component.
 10. A process forproviding a polymer that comprises ethylenic unsaturation, comprising:a) providing an initiating compound having the general formula

where M is a Group 1 metal and Q is a functional group that is free ofactive hydrogen atoms and that is bonded to the allylic C atom of theallyl anion through a P atom; b) introducing said initiating compound toa reaction vessel that comprises one or more organic liquids and one ormore ethylenically unsaturated compounds which comprise at least onepolyene; c) allowing said one or more ethylenically unsaturatedcompounds to polymerize, thereby providing said polymer; and d)optionally, while said polymer is in carbanionic form, allowing it toreact with a terminating compound, coupling agent or linking agent so asto provide terminal functionality to said polymer.
 11. The process ofclaim 10 wherein Q is a R¹ ₂P group where each R¹ independently is ahydrocarbyl group that is free of ethylenic unsaturation and active Hatoms.
 12. The process of claim 11 wherein each R¹ independently is anaryl group.
 13. The process of claim 10 wherein said at least onepolyene comprises one or more conjugated dienes.
 14. The process ofclaim 13 wherein said one or more ethylenically unsaturated compoundsfurther comprises at least one vinyl aromatic compound.
 15. The processof claim 10 wherein said one or more organic liquids comprise at leastone C₅-C₁₂ acyclic alkane.
 16. The process of claim 15 wherein said oneor more organic liquids is at least one C₅-C₁₂ acyclic alkane.
 17. Theprocess of claim 10 further comprising (e) recovering and isolating saidpolymer and (f) blending said polymer with ingredients that comprise atleast one particulate filler so as to provide a rubber compound.
 18. Theprocess of claim 17 further comprising vulcanizing said rubber compoundso as to provide a vulcanizate, said vulcanizate optionally being a tirecomponent.
 19. A process for providing a polymer that comprisesethylenic unsaturation, comprising: a) providing an initiating compoundhaving the general formula

where M is a Group 1 metal and Q is a functional group that is free ofactive hydrogen atoms and that is bonded to the allylic C atom of theallyl anion through a Sn atom; b) introducing said initiating compoundto a reaction vessel that comprises one or more organic liquids and oneor more ethylenically unsaturated compounds which comprise at least onepolyene; c) allowing said one or more ethylenically unsaturatedcompounds to polymerize, thereby providing said polymer; and d)optionally, while said polymer is in carbanionic form, allowing it toreact with a terminating compound, coupling agent or linking agent so asto provide terminal functionality to said polymer.
 20. The process ofclaim 19 wherein Q is a R¹ ₃Sn group where each R¹ independently is ahydrocarbyl group that is free of ethylenic unsaturation and active Hatoms.
 21. The process of claim 20 wherein each R¹ independently is aC₁-C₆ alkyl group.
 22. The process of claim 19 wherein said at least onepolyene comprises one or more conjugated dienes.
 23. The process ofclaim 22 wherein said one or more ethylenically unsaturated compoundsfurther comprises at least one vinyl aromatic compound.
 24. The processof claim 19 wherein said one or more organic liquids comprise at leastone C₅-C₁₂ acyclic alkane.
 25. The process of claim 24 wherein said oneor more organic liquids is at least one C₅-C₁₂ acyclic alkane.
 26. Theprocess of claim 19 further comprising (e) recovering and isolating saidpolymer and (f) blending said polymer with ingredients that comprise atleast one particulate filler so as to provide a rubber compound.
 27. Theprocess of claim 26 further comprising vulcanizing said rubber compoundso as to provide a vulcanizate, said vulcanizate optionally being a tirecomponent.